US3366065A

US3366065A - Supercharging of balanced hydraulic pump

Info

Publication number: US3366065A
Application number: US606933A
Authority: US
Inventors: Jr Carl A Pace; Nuss Christopher
Original assignee: Chrysler Corp
Current assignee: Old Carco LLC
Priority date: 1967-01-03
Filing date: 1967-01-03
Publication date: 1968-01-30
Anticipated expiration: 1985-01-30
Also published as: ES348831A1

Description

Jan. 30, 1968 c. A. PACE, JR, ETAL 3,366,065

SUPERCHARGING OF BALANCED HYDRAULIC PUMP Filed Jan. 5, 1967 4 Sheets-Sheet 1 fyd/uww,

irraxxvzxs'.

Jan. 30, 1968 c. A. PACE, JR., ET AL 3,366,065

SUPERCHARGING OF BALANCED HYDRAULIC PUMP 4 Sheets-Sheet 2 Filed Jan. 5, 1967 qg f zhv A msua NM, WYM

Jan. 30, 1968 c. A. PACE, JR, ETAL 3,366,055

SUPERCHARGING OF BALANCED HYDRAULIC PUMP Filed Jan. 5, 1967 4 Sheets-Sheet 5 Jan. 30, 1968 c. A. PACE, JR., ET AL 3,366,065

SUPERCHARGING OF BALANCED HYDRAULIC PUMP Filed Jan. 5, 1967 4 Sheets-Sheet 4 United States Patent 3,366,065 SUPERCHARGING OF BALANCED HYDRAULIC PUMP ABSTRACT OF THE DISCLOSURE A unidirectional inlet passage extends partially around the circumference of the rotor of a balanced roller pump from a first inlet port to a diametrically opposed second inlet port and is spaced from the rotor at least in part by a roller engaging cam ring defining the pumping chamber. Excess fiuid discharged from the pump i conducted via a bypass duct into the inlet passage adjacent the first inlet port and is biased directionally with respect to the first inlet port to proportion the supercharging of makeup fluid to the two inlet ports. A makeup duct conducts makeup fluid from a reservoir into a venturi restriction within the upstream end of the bypass duct. The total supercharging is maximized by centering the opening of the makeup duct into the bypass duct at a large acute angle with respect to the direction of the bypass flow into the upstream end of the bypass duct.

Related patents and applications Halsey Patents Nos. 3,236,566 and 3,247,803; Halsey copending application, Ser. No. 501,450, filed Oct. 22, 1965; Brady and Nuss applications Ser. No. 598,236, filed Dec. 1, 1966, and Ser. No. 598,426, filed Dec. 1, 1966.

Background and summary of the invention This invention relates to hydraulic pumps and in particular to improved means for supercharging the flow of fluid into the inlet ports of a balanced rotary pump, especially a roller pump for automobile power steering, having paired oppositely disposed inlet ports and similarly arranged outlet ports, although some of the advantages of the present invention are obtainable with other types of pumps.

As vehicle speeds have increased, emphasis has been placed on the economical production of high-speed and high-pressure engine driven automotive power steering pumps, along with greater pump efliciency and reliability. A significant problem in the development of such pumps, particularly of the roller type, has resulted from cavitation in the pump inlet system, with resultant noise and inefficiency. The problem of cavitation becomes particularly ditficult at high pump speed even at comparatively low output pressure, and at high output pressure even at moderate or intermediate pump speed.

An important object of the present invention is to provide a balanced rotary hydraulic pump having a pair of diametrically opposed inlet ports spaced by a pair of diametrically opposed outlet ports, in cooperation with a bypass valve arranged to receive excess fluid discharged from the outlet ports and to direct this fluid via a bypass duct into the upstream end of the pump inlet or fluid supply passage. The latter extends in the direction of rotor rotation circumferentially around the axis of the rotor from a first of the pair of inlet ports to the second to supply fluid thereto in succession. The bypass duct is designed in accordance with well-known venturi principles and is provided with an aspirator type fluid makeup port in communication with a reservoir, so that as the speed of bypass flow in the bypass duct increases (in consequence of increased pump speed or pump outlet pressure) the tendency to aspirate fluid into the bypass duct from the reservoir via the make-up port also increases. Thus a supercharging of fluid into the circumferential supply passage and thence into the inlet ports will increase with either increasing pump speed or outlet pressure.

It has been found that by virtue of the single circumferential supply passage and the consequent unidirectional flow to supply fluid to the first and second inlet ports in turn, the entire bypass flow is employed with a single venturi type aspirator and the supercharging eflect is optimized for the reason among possible others that the entire pump inlet flow is employed unidirectionally to effect the supercharging, thereby to minimize the ratio of venturi impedence to supercharging effectiveness, as compared to the conventional practice of bifurcating the inlet flow to the separate inlets and employing a separate venturi in one or both of the bifurcated inlet flow paths.

Another object is to provide a pump of the above character including means for biasing the flow into the upstream end of the supply passage so as to predetermine the proportion of the supercharging that will be effective at the first inlet port and thereby to predetermine the remaining supercharging effect that will be available at the second inlet port. By such a construction, the desired supercharging of the inlet flow at diametrically opposite sides of the pump is readily obtained, and if desired a slightly greater supercharging can be obtained at the second inlet port than at the first, as for example to accommodate for the greater pressure loss that would otherwise occur at the second inlet port during cold starting conditions as a result of fluid viscosity and friction.

Because of the trend toward ever decreasing underthe-hood space for the modern automobile, compactness in the steering pump as Well as economy of manufacture and installation are paramount considerations. It is accordingly another object to provide such a pump characterized by its compactness and economy of material, fabrication and assembly, in relation to its rated output, yet which is particularly quiet and eflicient in operation under all the varied and extreme conditions to which an automotive high-pressure power steering pump is normally subjected.

A specific object in accordance with the foregoing is to provide such a pump comprising a housing having a rotor journaled therein to carry a plurality of cylindrical pumping elements or rollers engageable with the interior wall of an out-of-round cam surface of the housing and extending around the rotor. The bypass valve comprises a fiuid pressure-actuated spool valve shiftable axially within the valve bore provided in the housing adjacent and parallel to the rotor bore and in communication with the pump outlet ports to receive a portion of the high pressure pump output. The bypass duct extends within the housing and communicates with the valve bore via a bypass port under the control of the valve spool to bypass the pump output in excess of the requirements of the power steering gear, the pump outlet ports being separated from the bypass port in accordance with the shifting of the spool valve.

In order to obtain the maximum supercharging eiiect from the bypass flow through the bypass duct, the makeup port opening into the bypass duct is located immediately proximate the opening of the bypass port into the valve bore. Also in order to maximize supercharging, it has been found, presumably in consequence of the combination of turbulence eifects and the direction of the fluid fiow from the valve bore during by-pass operation, that the make-up port should be located on the upstream side of a plane transverse to the valve bore 3 and through the center of the bypass port and should be centered on a line oblique to said plane and the axis of the valve bore, and preferably approximately midway between the latter plane and axis but closer to the latter axis.

Other and more specific objects are to provide such a construction wherein the pump inlet passage is spaced from the rotor by a cam ring. The latters radially outer circular periphery defines the inlet passage in part, whereas its radially inner periphery defines the aforesaid outof-round cam surface. The bypass bore extends radially from the valve bore and intersects the radially outer portion of the inlet end of the inlet passage substantially tangentially. The biasing means comprises a baflle oblique to the endwise flow from the bypass bore into the inlet passage for directing said flow into said inlet passage in a direction inclined radially inwardly.

Other objects are to provide such a construction wherein the pumping chamber is contained within a major portion of a cast housing member, whereas the bypass bore and valve bore are contained in a minor portion comprising an integral boss of the cast housing member. The axis of the valve bore is parallel to the rotor axi and perpendicular to the bypass bore, these bores extending into the boss from external openings suitably closed by plugs, the plug closing the bypass bore also having an integral surface comprising the aforesaid battle. A reservoir enclosure around the major cast housing member and boss cooperates therewith to provide a fluid reservoir, the make-up fluid duct comprising a bore extending in the boss from the reservoir and perpendicularly intersecting the bypass bore.

In accordance with the foregoing, optimum economy and compactness of construction are achieved in a roller pump characterized by particularly quiet and efficient operation.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Description of the drawings FIGURE 1 is an end elevational view of a pump embodying the present invention;

FIGURE 2 is a sectional view taken substantially in the direction of the arrows along the broken line 22 of FIGURE 3;

FIGURE 3 is a sectional view through the rotor and bypass valve taken substantially in the direction of the arrows along the broken line 3-3 of FIGURES 1 and 2;

FIGURE 4 is a fragmentary enlarged sectional view through the bypass and safety valves, taken substantially in the direction of the arrows along the line 4-4 of FIGURE 1;

FIGURE 5 is a sectional view taken substantially in the direction of the arrows along the line 55 of FIG- URE 3, showing details of the back pressure plate; and

FIGURE 6 is a sectional view taken substantially in the direction of the arrows along the line 6-6 of FIG- URE 5, showing the bypass valve in a partially open condition.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Description. of preferred embodiment Referring to the drawings a particular embodiment of the present invention is illustrated by way of example in a high pressure automobile power steering pump comprising a generally cup-shaped cast steel housing 10 open at its right end, FIGURE 3, to provide a circularly cylindrical pump chamber 11. The housing 10 provides an integral lower enlargement 10a containing an axially extending valve chamber 12 of circular cross-section also opening endwise in the same direction a the chamber 11. The left end of the housing 10 comprises a thickened hub 10b and a bore 13 coaxial with chamber 11 and containing an annular bearing 14 for a rotor shaft 15. The present pump has several features common to the pump described in Halsey Patents Nos. 3,236,566 and 3,247,803 and in the Halsey co-pending application, Ser. No. 501,450, filed Oct. 22, 1965, all assigned to applicants assignee, and reference thereto is hereby made for a possible better understanding of such features.

The outer end of the shaft 15 is connected to a hub 16 of a pulley 17 operatively connected with the automobile engine, as for example by means of a pulley belt, whereby the shaft 15 is rotated in accordance with engine speed to operate the pump. From the hub 16, the shaft extends inwardly through a seal 18 into chamber 11 and is secured therein to a rotor 20 by means of a key 21, whereby the rotor 20 rotates with shaft 15 and is freely slidable axially thereon. The circumference of the rotor 20 is provided with twelve uniformly spaced, axially extending and radially opening slots or notches 22, each containing a cylindrical roller 23. The sides of each notch 22 diverge radially outwardly from a width measured circumferentially less than the diameter of the roller 23 to a width greater than the roller diameter, so as to enable each roller to move freely radially within the corresponding notch 22 during operation of the pump as explained below.

The rollers 23 are restrained against radial movement by the out-of-round inner cylindrical cam surface 24 of a generally annular cam ring 25 having a cylindrical outer surface of circular cross-section coaxial with the rotor shaft 15 and fitting closely and axially slidably within the chamber 11. The rotor 20 and cam ring 25 space a front or base plate 26 from a rear pressure plate 27. The faces of the plates 26 and 27 which confront the cam ring 25 are flush with the juxtaposed faces of the latter and extend perpendicularly to the axis of the rotor 15. In order to allow freedom of rotation of the rotor 20, its axial length in FIGURE 3 is slightly less than the axial length of the ring 25 by approximately .0013 for example. Similarly the axial length of the rollers 23 is approximately equal to the axial length of the rotor 20.

The outer cylindrical surfaces of the plates 26 and 27 fit closely and axially slidably within the chamber 11 and the outer face of plate 26 fits flush against the base 11a of the chamber 11. The plates 26 and 27 cooperate to confine the rotor 20 within a pumping chamber bounded circumferentially by the cam surface 24 and are maintained in circumferential alignment with the ring 25 by means of an axially extending pin 28 which extends snugly through aligned openings in the ring 25 and plates 26, 27 and is confined at its left end within the wall of housing 10.

The rear or endwise opening of the chamber 11 is closed by a plug 31 secured in position by a wire ring 32 partially embedded in the housing 10. Annular O-

rings

33 and 34 around the plug 31 and pressure plate 27 respectively prevent axial leakage of high pressure fluid. The plate 27 is urged axially against ring 25 by a coil spring 35 seated within a central pocket 30 in plug 31, thereby to seat the plate 26 against the wall 11a and to seat the ring 25 between the plates 26 and 27 in fluid sealing relationship, which relationship is enhanced by the pressure of the pump discharge fluid contained within a fluid discharge header 36. The latter is located between plate 27 and plug 31 and opens through a high pressure port 37 in the housing 10 into the right end of valve chamber 12. Extending rightwardly from the rotor 20 in FIGURE 3 is a shaft stub end 15a of shaft 15, which projects coaxially into a cup-shaped pocket 38 in plate 27, the pocket 38 containing a bearing 39 for the stub 15a. The base of pocket 38 comprises a seat for spring 35. An annular groove 40 in the shaft 15 adjacent the right edge of rotor 20 carries a wire ring 41 which serves as a retainer to prevent leftward separation of the shaft 15 from the pump assembly. A similar groove 42 and wire ring 43 are provided adjacent the left edge of rotor 20.

Referring to FIGURE 2, the cam surface 24 comprises a pair of diametrically opposed 30 seal arcs 45 and 45a of constant diameter. Mutually spacing the seal arcs 45 and 45a are another pair of diametrically opposed 50 dwell arcs 46 and 46a of constant radius somewhat larger than the radius of the arcs 45 and 45a. Between each small constant radius seal are 45 or 45a and the next adjacent large constant radius dwell are 46 or 46a, measured clockwise in FIGURE 2, is a 55 inlet are 47 or 47a respectively of gradually increasing radius. Similarly, between each large diameter dwell are 46 or 46a and the next clockwise adjacent small diameter seal are 45 or 45a is a 45 outlet arc 48 or 4811 respectively of gradually decreasing radius. The terminals of the inlet and outlet arcs merge tangentially with the juxtaposed terminals of the seal and dwell arcs of constant radii, the rate of change of radius for each of the inlet and outlet arcs being slight near the leading and trailing ends of these arcs and gradually increasing to their mid-regions, particularly in regard to the inlet arcs 47 and 47a wherein the rate of change of radius is comparatively small along the leading and trailing thirds of the inlet arcs and gradually increases toward the mid-region, such that the rate of change of radius is comparatively large throughout the middle third of the inlet arcs.

At the sectors of the diametrically disposed inlet arcs 47 and 47a, the pump chamber 11 is enlarged to provide a pair of fluid inlet recesses or chambers 49 and 49a respectively, FIGURE 2, which extend axially in the housing at locations adjacent and radially outwardly of plates 26 and 27 and ring 25, as indicated in FIGURE 3, and intersect a circumferentially extending inlet header 50 coaxial with rotor 20. The header 50 extends within the housing 10 at a location radially outwardly of and partially overlapping ring 25 and plate 27 which define its inner wall. The upstream or inlet end 51 of the header 50 communicates with the valve chamber 12 to receive fluid therefrom via a generally tangentially extending bypass duct 52 in the housing 10, FIGURES 2, 4 and 5, as described below.

Opening axially into the pump chamber 11 from the inlet recesses 49 and 49a respectively are a pair of radially outer inlet ports 53 and 53a formed in plate 26. A similar mating pair of outer inlet ports 53 and 53a are located in plate 27 directly opposite the corresponding ports 53 and 53a. These outer inlet ports open axially toward the rotor 20 and also open radially outwardly into their respective recesses 49, 49a and thus into inlet header 50 to receive inlet fluid, FIGURES 2 and 3, and partially overlap the axial ends of the rollers 23 and the radially outer portions of the rotor notches 22 to supply the latter with fluid as they sweep across the inlet cam arcs 47 and 47a. Radially inwardly of the ports 53 and 53a are a pair of inner inlet ports 54 and 54:: formed in plate 26 to receive fluid from inlet recesses 49 and 49a and to discharge the fluid axially into the rotor notches 22 at locations radially inwardly of the rollers 23. Similar inner inlet ports 54' and 54a are provided in plate 27 to confront rotor 20 directly opposite the

ports

54 and 54a respectively. The transverse areas of the inlet ports of each axially opposed pair are substantially identical, so as to maintain the rotor 20 and rollers 23 in hydraulic balance. As indicated in FIGURE 2, the radially

outer inlet ports

53, 53a, 53 and 53a are partially restricted with respect to the radially

inner inlet ports

54, 54a, 54' and 54a; so as to effect proper timing of the movement 6 of the rollers 23 within their notches 22 and to prevent the rollers 23 from falling away from the rising cam surface 24 during the inlet cycle, as described below.

At the region of the discharge cam arcs 48 and 48a, the pressure plate 27 is provided with a pair of axially extending outer and inner

arcuate discharge ports

55', 56 and 55a, 56a respectively,- which discharge into header 36, FIGURE 3. The radially outer discharge ports 55, 55a partially overlap the ends of the rollers 23 and the radially outer portions of the notches 22, whereas the radially inner discharge ports 56', 56a open from the inner portions of the notches 22 radially inwardly of the rollers 23, to receive fluid from the notches 22 upon inward movement of the rollers 23 during operation of the pump. Axially opposite the discharge ports 55', 55a, 56' and 56a are

pressure balancing recesses

55, 55a, 56, and 56a respectively, formed in the surface of plate 26 confronting the rotor 26 to provide areas substantially equal to the corresponding areas of the axially opposed discharge ports in plate 27, so as to maintain the rotor 20 and rollers 23 in hydraulic balance except as explained below.

It is to be noted in the above regard that the inner outlet ports 56' and 56a in plate 27 extend circumferentially in the direction of rotation appreciably beyond the trailing ends of the mating recesses 56 and 56a in plate 26 and overlap the axial ends of the rollers 27 within the trailing third of the outlet arcs 48 and 48a, FIG. 2, thereby to provide an unbalanced high pressure force axially against these rollers. It has been found that such axial end loading of the rollers in the trailing portion of the outlet arcs of decreasing radius contributes significantly to roller stability in a high pressure balanced roller pump, reducing both noise and wear during highspeed operation. In order to compensate for the circumferential elongation of the ports 56' and 56a, their ra dial dimensions are reduced, so that their total cross sectional area remains substantially equal to the total cross sectional area of the balancing recesses 56 and 56a. Accordingly the rotor 20 is maintained in hydraulic balance.

Slidable axially within valve chamber 12 is a hollow cylindrical slide or spool valve 58 urged rightward against the pump discharge pressure by means of a coil spring 59 seated under compression between the left ends of chamber 12 and valve 58, FIGS. 3 and 4. The chamber 12 comprises a bore extending leftward in housing portion 10a and is sealed by a closure 60 retained in place by a C-ring 61 partially embedded in the housing side wall. A seal 62 around the periphery of the closure 60 prevents endwise leakage of the fluid from the housing enlargement 10a. Extending inwardly as an integral portion of the closure 60 is a stop 63 adapted to limit rightward movement of valve spool 58.

The bypass duct 52 opens into the bore 12 at a bypass port 64 near the upstream end of bore 12 and is connected by means of a fiuid make up duct 65 with a reservoir 66 for supercharging the inlet flow of hydraulic fluid into duct 52. The diameter of the latter is reduced with respect to the diameter of valve bore 12 to comprise a venturi restriction between bore 12 and the enlarged inlet 51 for header 50, FIG. 5. Also the bypass duct 52 comprises a bore into housing enlargernent 10a from the right in FIG. 5, the axes of the

bores

12 and 52 intersecting at right angles and the remote or outer end of bore 52 being closed by plug 67 having an inner flow biasing cam surface 68 projecting into the inlet'51 obliquely to the axis of bore 52. Thus the

cam element

67, 68 serves both to direct the flow of supercharged fluid radially inwardly and generally tangentially into inlet header 50 and also to close the outer end of the bypass bore 52.

As shown in FIG. 6, the axis of make-up duct 65 intersects bypass duct 52 at right angles as closely to bypass port 64 as feasible and converges in the direction of leftward opening movement of spool 58, FIGURE 6, toward a plane containing the axes of both

bores

12 and 52. It has been found that if the axis of make-up bore 65 intersects the aforesaid axial plane at an acute angle A, which is preferably slightly less than 45 or approximately 35 as shown, optimum supercharging or acceleration of the make-up fluid entering inlet 51 from reservoir 66 via

bores

65 and 52 is achieved when the high pressure fluid discharged from header 36 into valve bore 12 via port 37 causes leftward opening movement of valve spool 58 from the most rightward or trailing edge portion 64a of bypass port 64, FIGURE 6. The make-up bore 65 may enter bypass bore 52 from either side of the aforesaid plane common to the axes of both

bores

12 and 52 and at a location centered in the midregion of the arc between this plane and a normal thereto, but preferably closer to said plane. By virtue of the parallel axes of the rotor 20 and valve 58 and the intersecting axes of the

bores

52 and 65 as described, in combination with the biasing cam 68 and inlet header 50 as shown, a particularly compact and eflicient pump and supercharging arrangement is achieved.

In order to supply high pressure working fluid at a metered rate to the automobile power steering gear 68, FIGURE 1, a primary passage 69 for the working fluid is bored into the housing a through the valve port 37 to communicate with the latter and to receive the pressurized output fluid from the header 36. The open end of the bore 69 is sealed by a closure 70. A second bore 71 in the housing 10a intersects the bore 69 downstream of the valve port 37 and communicates with the valve bore 12 at a secondary port 72. A tubular fitting 73 extends eoaxially within the bore 69 to provide a closure for the radially outer portion of the bore 71 and also to provide a first restricted metering orifice 74 which opens axially endwise into a delivery passage 75. A portion of the latter is bored into the housing 10a and communicates with valve bore 12 at a delivery port 76 downstream of the secondary port 72. The delivery passage 75 extends to the hydraulic motor of the power steering gear 68 to supply pressurized working fluid thereto in a conventional manner, the exhaust fluid from the motor being discharged via 75a into the reservoir 66 as indicated, FIGURE 1. The tubular insert 73 is also provided with a restricted lateral metering orifice 77 opening into the portion of bore 71 which in turn opens at 72 into the valve bore 12.

The valve spool 58 is provided with an annular bypass land 78 at its upstream end for controlling the communication between the valve port 37 and bypass port 64 in accordance with axial shifting of the spool 58 as described below. Similarly a second annular land 79 of the spool 58 controls the opening of the secondary port 72 into the valve bore 12. An annular third or guide land 80 spaced from the land 79 by an annular recess 81 serves as a guide for the spool 58 in bore 12 and is provided with a restricted trigger orifice 82 extending axially therethrough into a downstream chamber portion 83 of the bore 12. The valve biasing spring 59 seated against the guide land 80 urges the spool 58 rightward against the stop 63 with a substantially constant force within the range of movement permitted.

It is apparent from the construction shown that the high pressure directed against the upstream end surface area of the spool valve 58 is balanced by the combined forces of the spring 59 and the pressure in the downstream chamber 83 against the downstream end surface area of the spool 83, such that a constant pressure differential across orifice 74 is maintained as determined by the force of spring 59. In the event that the pressure differential across metering orifice 74 tends to vary, the valve spool 58 will shift correspondingly to increase or decrease the communication of bypass bore 52 with the valve port 37. In consequence of the constant pressure differential across metering restriction 74, a constant flow of working fluid into the delivery passage and to the gear 68 will be supplied at all times during operation of the pump at moderate engine speeds as described below, regardless of the pressure in passage 75 determined by the power demands of the gear 68. It is also to be noted that a secondary restricted passage through restriction 77, port 72, and port 76 provides a limited bypass flow of the working fluid around the restriction 74 into delivery passage 75 during operation at moderate engine speeds. Obviously the pressure differential across the secondary restricted passage will be the same as the pressure differential across the parallel orifice 74.

In a typical power steering gear the combined flow through restrictions 77 and 74 will be in the neighborhood of approximately 2.7 gals. per minute when port 72 is open as in FIGURE 4. The excess pump output will be bypassed into port 64 upon leftward shifting of valve spool 58. During high speed operation of the vehicle engine and increased pump output, port 72 is closed by land 79 upon leftward movement of spool valve 58. Thus at high vehicle speeds ordinarily above 60 mph. when the power requirements of the gear 68 are at a minimum, the flow of working fluid into delivery passage 75 is reduced sharply to approximately 1.5 gals. per minute by the closing of the secondary passage through port 72.

During the operation described thus far, there is no fluid flow through trigger orifice 82 except to accommodate transitory shifting of valve 58, whereupon orifice 82 effects a dash-pot action to damp sudden valve movements. Accordingly, the fluid pressure in the downstream chamber 83 will usually be substantially the same as the pressure of the working fluid in delivery passage 75.

In order to prevent the development of an unsafe pressure in the delivery conduit or passage 75 in the event of an excessive power demand by the motor 68, a fluid pressure relief system is provided comprising a coaxial bore 34 in the spool 58, which opens into chamber 83. The bore of a tubular valve insert secured within the open end of bore 84 is normally closed at its inner end by a ball check valve 86. The latter is maintained in a seated position against the end of tube 85 to close the bore 84 by means of a spring retainer 87 urged leftward against the ball 86 by a spring 88 seated under compression against a flange of the retainer 87 and the closed right end of bore 84. An annular recess 89 in the outer periphery of spool 58 communicates with the bypass port 64 and is in turn connected with the bore 84 by a plurality of radial bores 90 to discharge fluid from the chamber 83 into bypass port 64 upon opening or unseating of valve 86 against the force of spring 88 in response to pressure at an upper limit in chamber 83.

Upon the unseating of valve 86, a small quantity of fluid will be discharged into bypass 52 through bore 84. By virtue of the restriction of trigger orifice 82, the pressure in downstream chamber 83 will be immediately reduced to enable leftward shifting of valve spool 58, thereby to increase the opening of bypass port 64. In consequence, a comparatively insignificant fluid flow around check valve 86 can result in a comparatively large rate of increase in the bypass flow around land 78. Reference is hereby made to the aforesaid copending applications of Brady et al. for a more detailed explanation of the structure and operation of the flow control bypass valve mechanism.

The reservoir 66 is defined in part by the exterior of housing 10 and is enclosed by an outer cup-shaped shell or reservoir housing 91 fitted over the rear or right end of the housing 10, FIGURE 3.

Near its front end, the housing 10 has an integral annular seal retaining groove 92 eccentric with respect to rotor 20 and containing an annular O-ring seal 93. The latter is under compression between the juxtaposed por tions of the housing 10 and shell 91 to prevent fluid leak 9 age from the reservoir 66. Forwardly of the seal 93, the shell 91 terminates in an outturned reinforcing flange 94.

The pump is pivotally mounted on the vehicle engine by means of a bracket 95 pivotally secured to the engine and bolted to a pair of housing mounts 96 integral with the housing enlargement 10a forwardly of the reservoir shell 74. A portion of the bracket 95 extends around to the rear of the housing 10 and is bolted to boss 97 thereof by means of bolt 98 which extends through the bracket 95 and reservoir shell 91 to clamp these members together. Leakage around the bolt 98 is prevented by an annular seal 99 compressed between shell 91 and portions of the boss 97.

An upper annular flange 100 of the shell 91 defines an opening into the lower end of a cylindrical expansion chamber 101 welded to flange 100. The upper end of chamber 101 is closed by a removable cap 102, whereby hydraulic fluid lost from the system by leakage may be readily replenished. Normally the fluid level will be maintained at approximately the level of the base of flange 100.

High pressure fluid which tends to leak radially from the discharge ports 55', 56', 55a, 56a and pressure balancing recesses 55, 56, 55a, 56a toward the shaft is conducted from the right end 15a of the latter by a bleed conduit 103 bored in the plate 27 from the inlet port 54a to the rear end of cylindrical chamber 38, FIGURE 3. Similarly, fluid leaking axially along shaft 15 to seal 18 is returned to the reservoir 66 by means of a suitable bleed conduit formed in the housing 10, so that operation of the pump does not tend to suck air axially inwardly through the seal 18, as for example, into one of the inlet ports. The inner end of the stub shaft 15a may be drained directly to the inlet port 54a as illustrated because this end is positively sealed from the atmosphere.

In order to effect a smooth transition in the fluid pressure as the low pressure inlet fluid is carried along the seal arcs 46, 46a to the high pressure outlet arcs 48, 48a, the leading edges of the

inner discharge ports

56 and 56a are in communication with compression recesses 104 and 104a respectively in the back plate 27. These recesses are generally triangular in their elevational views, FIGURE 2, and diverge in the direction of rotor rotation from their apices to their corresponding inlet ports. Such recesses may be provided alternatively in the plate 26 and are effective to reduce noise during operation.

In operation of the structure described, upon clockwise rotation of the rotor 20 in FIGURE 2, as the rollers 23 ride along cam 24 at the

inlet sectors

47 and 47a of increasing radius, fluid is forced into the gradually expending volume of the notches 22 unoccupied by the rollers 23 and is carried across the dwell arcs 46 and 46a of large constant cam radius and discharged under pressure through the ports 55', 56', and 55a, 56a by virtue of the decreasing cam radius at the outlet arcs 48, 48a. The inlet arcs 47, 47a are separated from the adjacent discharge sectors 48, 48a by at least one roller 23 within each of the seal and dwell arcs 45, 45a, 46, 4661 at all times. In this regard, a seal is effected at the engagement of each roller 23 with the cam arcs of constant radius, the outlet arcs of decreasing radius, much of the inlet arcs of increasing radius, and the edges of the notch 22 as described below. By virtue of the construction described the extent of the seal arcs 45, 45a and dwell arcs 46, 46a spacing the inlet ports and discharge ports and the circumferential extent of the inlet and discharge ports can be readily dimensioned to minimize bypass leakage between the high and low pressure regions of the pump chamber 11 and to facilitate filling of the notches 22 at the regions of the inlet cam arcs whereby the problems of cavitation are minimized.

This latter function is aided by the unidirectional fiow in inlet header 50 from its inlet 51 adjacent to the up stream inlet porting system at the inlet arc 47, i.e. the

inlet ports

53, 53, 54, 54, to the diametrically opposed downstream inlet ports at the arc 47a, in cooperation with the venturi action of the bypass duct 52 and the arrangement of the makeup bore 65 and flow directional biasing cam 68 described to effect a superior supercharging of the make-up fluid into inlet 51. Also the wrap around reservoir shell 91 enables the provision of a short low resistance make-up duct 65 directly into the bypass bore 52 from the reservoir 66.

In further explanation of the pump operation, the notches 22 and rollers 23 at the positions a through f, FIGURE -2, will also be referred to herein as the notches or rollers a through 1 respectively. At the position shown, the roller a is leaving the outlet cam arc 48a of decreasing radius and is about to enter the seal cam are 4561 of constant radius. Roller a is thus uniformly subjected to high pressure fluid within its rotor notch 22 and has no fluid sealing function, although it is in contact with the trailing edge of its rotor notch 22 and arc 48a. It is also in fluid contact with unbalanced pressure within recess 560, which urges roller a axially leftward in FIG- URE 3. The clearance between the rotor 20 and surface of cam 24 at all locations conducts fluid into the space between rolls a and b to fill that space with high pressure fluid and urge roller b into fluid sealing engagement with both the cam surface of seal arc 45a and the leading edge of its notch 22 along axially extending lines of tangency, thereby to separate the low pressure fluid at inlet are 47 from the high pressure fluid at outlet arc 48a.

Upon clockwise rotation of the rotor 20 approximately 2 in FIGURE 2, the rollers a and b will enter the seal and inlet arcs respectively. By reason of the contact of roller b with the leading edge of its notch 22, and the contact of roller a with the trailing edge of its notch 22, the roller b will enter the inlet are 47 of increasing radius very slightly before the roller a enters the seal arc 45a of constant radius. Accordingly, the high pressure immediately behind or at the counterclockwise side of rollet [2 will begin to decrease very gradually at first to avoid shock and roller instability and then at an accelerated rate as roller b continues to move radially outwardly along the inlet arc of increasing radius, which movement is enhanced by the residual high pressure in the notch b radially inwardly of the roller b. Also immediately before roller a enters the seal arc 45a, the trailing edge of its notch 22 seals off the high pressure fluid from the rotor balancing and roller biasing recess 56a. Thus as the high pressure at the counterclockwise of roller b decreases, roller 11 will be moved clockwise into sealing engagement with both the leading edge of its notch a and the seal cam surface 45a, thereby to assume the sealing function of roller b in FIGURE 2 as roller a moves along the seal arc 45a.

After roller b moves clockwise about 10 along the inlet arc 47 toward the central region of the latter whereat the rate of increase of radius is most rapid and whereat the difliculty of maintaining the roller in sealing contact with the inlet arc is most serious, i.e about a fifth or sixth of the length of the inlet arc, the leading edge of notch b will intersect the leading ends of the

inner inlet ports

54a and 54a. By this time, the pressure in notch b will have been gradually reduced to the pressure of the inlet fluid entering from the radially outer inlet ports 53 and. 53 and leaking counterclockwise via the clearance between rotor 20 and inlet arc 47, so that roller b will have lost its sealing function (now assumed by roller a) and will have been moved into driven engagement with the trailing edge of its notch 22.

By virtue of the aforesaid restriction afforded by the outer inlet ports 53 and 53 with respect to the inner inlet ports 54' and 54, the opening of the latter ports into the notch b will establish a radially outwardly directed pressure force on roller b, assisting the latters centrifugally urged radial outward movement and maintaining it positively in engagement with the inlet cam surface 47 at all times. After moving approximately 20 along the inlet arc 47, or for more than one-third of its distance and almost to the position of roller c, the sealing engagement between the cam surface and roller b intersects the outer inlet ports 53 and 53', whereby the roller b will then assume the positions of rollers c and d in turn and the cavity between the surface of cam 24 and rotor 20 from roller b to roller e will be completely filled with the inlet fluid. Also the opening of the inner ports 54 and 54' into the notch b assures that the roller b will be in said driven engagement with the trailing edge of its notch b. By virtue of delaying direct opening of the notch b into communication with

inner inlet ports

54 and 54 until after the roller b has moved along approximately one-fifth of the length of the inlet arc, and by further delaying the opening of the outer inlet ports 53 and 53' into the rotor notch 22 at the counterclockwise side of roller b, rapid decompression of the notch b and consequently noise are avoided without recourse to the customary decompression notches.

As the roller d moves toward the position of roller e, the roller seal at the cam surface 24 will cut off the outer inlet ports 53 and 53' slightly before the trailing edge of the notch d cuts off the inner inlet ports 54- and 4. Simultaneously or slightly later the leading edge of the latter notch will intersect the leading tip of the compression recess or notch 104. This will occur after the roller a has moved several degrees, i.e. approximately along the dwell are 46 of constant radius to assure complete filling of the space on the counterclockwise side of roller e. On continued clockwise movement of roller d, the space between the same and roller (2 will gradually attain the high pressure of the outlet ports and roller d will assume the scaling function of roller e to separate the high pressure at the outlet are 48 from the low pressure at the inlet arc 47. By virtue of the foregoing, cavitation and noise during the inlet operation of the pump are substantially avoided.

The high pressure fluid discharge within the header 36 reacts against and holds the pressure plate 27 in sealing engagement with the cam ring 25, the latter in turn being urged in sealing engagement against the front plate 26 which is thus urged in sealing engagement against the base wall 11a, all with a force which is proportional to the pump discharge pressure. Accordingly leakage from the high pressure outlet arc regions 48, 48a radially toward shaft and circumferentially toward the low pressure inlet arcs 47, 47a is substantially eliminated. Fluid that does leak through the high resistance leakage paths provided, as for example to the inside of seal 18, will be at low pressure and is returned to reservoir 66 or the fluid inlet system as explained above.

We claim:

I. In combination (a) a hydraulic pump having 1) inlet and outlet means and (2) operative to pump low pressure inlct fluid from said inlet means to said outlet means under pressure,

(b) an external working fluid circuit having (1) a high pressure receiving end connected with said outlet means to receive pressurized fluid therefrom and 2) a low pressure fluid return end,

(c) a valve chamber in communication with said out let means to receive pressurized fluid therefrom and having (1) a bypass port for discharging pressurized bypass fluid from said valve chamber,

(d) a bypass duct opening into said valve chamber at said bypass port to receive said pressurized bypass fluid and communicating with said inlet means to discharge said pressurized bypass fluid thereinto,

(e) fluid actuated valve means responsive to the output of said pump and the pressure in said external circuit for progressively opening or closing said bypass port substantially in one direction or the opposite with respect to an edge portion thereof to control the communication between said outlet means and bypass duct,

(f) means for supplying make-up fluid to said bypass duct comprising (1) a make-up port opening into said bypass duct immediately downstream of said bypass port and (2) a make-up duct in communication with said return end of said external circuit to receive low pressure make-up fluid therefrom and opening into said bypass duct at said make-up port to accelerate said make-up fluid by injection into the flow of said pressurized bypass fluid,

(3) the angular position of said make-up port measured from said edge portion of said bypass port around the periphery thereof being between said edge portion and a line passing through the central region of said bypass port perpendicularly to both said direction of opening of said bypass port and the direction of said flow of pressurized bypass fluid therethrough adjacent said edge portion.

2. In the combination according to claim 1, said angular position of said make-up port being approximately at the mid-region between said edge portion and line.

3. In the combination according to claim 2, the angular position of the center of said make-up port being about 35 around the periphery of said bypass port measured from said edge portion.

4. In the combination according to claim 1, said bypass valve chamber being cylindrical and having its longitudinal axis extending in said direction of opening of said bypass port, said bypass valve means comprising a reciprocable fluid actuated spool valve movable axially in said cylindrical chamber to progressively open said bypass port and movable in the opposite direction to progressively close the latter, said angular position of said make-up port on the periphery of said bypass duct being approximately at the mid-region of said periphery between a predetermined plane and line, but closer to said edge portion of said bypass port than to the intersection of said line with the periphery of said bypass port, said predetermined plane containing the longitudinal axis of said cylindrical valve chamber and the center of said bypass port, said predetermined line passing through the center of said bypass port perpendicularly to said plane.

5. In the combination according to claim 4, said pump comprising a balanced pump having a housing containing said valve chamber and inlet and outlet means, a pumping chamber within said housing, said inlet and outlet means including a succession of inlet and outlet ports mutually spacing each other around the periphery of said pumping chamber and communicating therewith to supply said inlet fluid thereto and to receive said pressurized fluid therefrom, pumping means operable within said pumping chamber for pumping said inlet fluid from each inlet port to the next successive outlet port under pressure, said inlet means including an inlet passage communicating with the succession of inlet port to supply said inlet fluid thereto and extending in said housing partially around said pumping chamber from an upstream end beginning adjacent the first of said succession of inlet ports to a downstream end terminating adjacent the last of said succession of inlet ports, said bypass duct opening into said upstream end substantially tangentially to said inlet passage, and biasing means for deflecting the fluid flow from said bypass duct toward said pumping chamber and into said inlet passage in the downstream direction of extension thereof comprising a battle at said upstream end obliquely confronting the outlet of said bypass duct.

6. In the combination according to claim 4, said pump having a housing containing said valve chamber and inlet and outlet means, a cylindrical pumping chamber in said housing adjacent said valve chamber and having its longitudinal axis parallel to the longitudinal axis of said valve chamber, a rotor within said pumping chamber and having its axis of rotation parallel to said pumping chamber axis, said housing including a cam ring around the periphery of said rotor and having an inner peripheral cam surface defining the outer periphery of said pumping chamber, said inlet and outlet means including inlet and outlet ports respectively opening axially into said pumping chamber at circumferentially spaced locations to supply said inlet fluid to said pumping chamber and to receive said pressurized fluid therefrom respectively, pumping elements carried by said rotor and cooperable therewith and with said cam surface for pressurizing said inlet fluid and pumping the same from the inlet port to the outlet port upon rotation of said rotor, said bypass duct extending within said housing adjacent and radially outwardly of said cam ring approximately perpendicularly to the axis of said valve chamber and opening endwise into the upstream end of said inlet means in a direction approximately at right angles to an axial plane of said rotor and cooperating with said inlet means to comprise a venturi tube having its throat at the region of said make-up port, and biasing means for deflecting the direction of fluid flow from said bypass duct toward said pumping chamber in a direction oblique to the last named plane and approximately parallel to a second plane which is normal to said rotor axis comprising a baflle defining in part said upstream end of said inlet means and obliquely confronting the outlet of said bypass duct.

7. In the combination according to claim 6, said housing comprising a major generally cylindrical portion having said pumping chamber therein and having an integral radially extending boss containing said valve chamber and bypass duct, said boss being appreciably smaller than said major portion.

8. In the combination according to claim 7, reservoir cover means cooperable with the exterior surface of said housing to form a reservoir chamber comprising the low pressure return end of said external circuit in the space adjacent said boss, said makeup duct opening through the sidewall of said bypass duct into said reservoir chamber to receive fluid therefrom.

9. In the combination according to claim 6, said pump comprising a balanced pump, said inlet and outlet means including a succession of inlet ports and a corresponding succession of outlet ports opening into said pumping chamber and mutually spacing each other circumferentially around said pumping chamber, said inlet ports opening axially into said pumping chamber, said pumping elements cooperating with said rotor and cam surface for pressurizing said inlet fluid and pumping the same from each inlet port to the next successive outlet port upon rotation of said rotor, said inlet means including an inlet passage extending circumferentially within said housing partially around said pumping chamber from said upstream end adjacent the first of said succession of inlet ports and terminating downstream adjacent the last thereof and communicating with said inlet ports to supply said inlet fluid thereinto.

10. In the combination according to claim 1, said angular position of said make-up port being approximately at the mid-region between said edge portion and line, said pump comprising a housing having a cylindrical pumping chamber, pumping means rotatable within said pumping chamber about an axis parallel to the axis of said pumping chamber for pumping inlet fluid from said inlet means to said outlet means under pressure, said bypass duct comprising a bore in said housing opening into an upstream end of said inlet means substantially tangentially to said rotor.

11. In the combination according to claim 10, a cam ring within said housing around said pumping means and having an inner peripheral surface defining the inner surface of said pumping chamber, said inlet means including an inlet passage extending from said upstream end circumferentially partially around said rotor and spaced radially therefrom by said cam ring, the outer peripheral surface of said cam ring defining in part the wall of said inlet passage, said inlet means also including a succession of inlet ports spaced circumferentially around said pumping chamber, said inlet ports connecting said inlet passage With said pumping chamber and opening axially thereinto to supply said inlet fluid thereto, the upstream end of said inlet passage being adjacent the first of said succession of inlet ports, said inlet passage extending circumferentially from its upstream end to its downstream end adjacent the last of said succession of inlet ports to supply said inlet fluid thereto.

12. In a hydraulic pump,

(A) a housing containing a pumping chamber,

(B) a succession of inlet ports and a corresponding succession of outlet ports opening into said chamber and mutually spacing each other around an axis thereof,

(C) pumping means within said chamber for'purnping inlet fluid from each inlet port to the next successive outlet port under pressure,

(D) an inlet passage extending within said housing partially around said axis and communicating with said succession of inlet ports to supply said inlet fluid thereto,

(1) said inlet passage extending downstream from an inlet end thereof adjacent the first inlet port of said succession thereof and terminating at a downstream end adjacent the last inlet port in said succession,

(E) means for supplying pressurized inlet fluid into said inlet end of said inlet passage to supercharge said inlet ports, and

(F) means for prorating the pressure of said inlet fluid at said first inlet port with respect to the others in said succession thereof comprising (1) a battle (a) defining in parts said inlet end of said inlet passage and (b) arranged obliquely with respect to the direction of flow of said pressurized inlet fluid into said inlet end for biasing said flow therein at a predetermined angle with respect to said first inlet port and toward a predetermined location measured downstream from said inlet end.

13. In the combination according to claim 12, said inlet passage comprising a partial annulus extending partially around said periphery, said means for supplying said pressurized inlet fluid including a duct opening endwise into said inlet end of said inlet passage in a direction substantially at right angles to a radial plane containing said axis, and said baflle comprising a surface oblique to the last named direction for directing said pressurized inlet fluid obliquely inwardly toward said chamber and substantially parallel to a plane at right angles to said axis.

14. In the combination according to claim 12, said inlet passage extending arcuately partially around said axis, said housing including a boss offset outwardly from said axis, said means for supplying said pressurized inlet fluid including a bore entering said boss at an exterior opening and intersectng said inlet passage substantially tangentially thereto at said inlet end thereof, and said baflle including a plug closing said exterior opening.

15. In the combination according to claim 14, an external fluid working circuit having a high pressure fluid receiving end connected with said outlet ports to receive pressurized fluid therefrom and having a low pressure fluid return end, said inlet passage extending partially around said axis comprising a partial annulus, a valve chamber in said boss, means connecting said valve chamber with said outlet ports, said bore comprising a bypass duct having an upstream end opening into said valve chamber to receive said pressurized fluid, a fluid pressure actuated bypass valve in said valve chamber responsive to the output of said pump and the flow in said external circuit for controlling the communication between said outlet ports and said bypass duct, and a make-up duct in communication with siad return end of said external circuit to receive low pressure make-up fluid therefrom and opening into said bypass duct downstream of said valve chamber to accelerate said make-up fluid by injection into the flow of said pressurized fluid in said bypass duct.

16. In the combination according to claim 15, said valve chamber comprising a second bore entering into said boss at an exterior opening and extending substantially parallel to said axis of said pumping chamber and perpendicular to the bore comprising said bypass duct.

17. In the combination according to claim 12, said inlet passage extending arcuately partially around the periphery of said pumping chamber, said means for supplying said pressurized inlet fluid comprising a bypass bore within said housing intersecting the radially outer surface of the inlet end of said inlet passage substantially tangentially thereto, and said baffle comprising means for directing the flow of said inlet fluid from said bypass bore into said inlet passage in a direction substantially parallel to a plane at right angles to said axis inclined both radially inwardly and downstream within said inlet passage.

18. In the combination according to claim 12, said pumping means including a rotor within said chamber, a cam ring having an inner cam surface around the axis of rotation of said rotor and defining the periphery of said chamber, and pumping elements carried by said rotor and cooper-able therewith and with said cam surface for pumping said inlet fluid from each inlet port to the next successive outlet port, said inlet passage extending partially around the radially outer surface of said cam ring, the latter surface defining in part the radially inner wall of the inlet passage, and said means for supplying said pressurized inlet fluid comprising a bypass bore within said housing intersecting the radially outer surface of the inlet end of said inlet passage substantially tangentially thereto.

19. In the combination according to claim 18, said rotor having a plurality of radially opening notches spaced around its periphery, said pumping elements comprising a corresponding plurality of rollers operable within said notches respectively and adapted to move along said cam surface in fluid sealing engagement therewith, each inlet port having a portion in communication with said inlet passage and also having a portion extending radially inwardly of said cam surface adjacent an axial end of said rotor and communicating axially with said pumping chamber to supply said inlet fluid axially thereinto.

20. In the combination according to claim 18, an external fluid working circuit having a high pressure receiving end connected with said outlet ports to receive pressurized fluid therefrom and having a low pressure fluid return end, fluid actuated bypass valve means responsive to the output of said pump and the flow in said external circuit for connecting said outlet ports and bypass bore and controlling the flow of pressurized bypass fluid into the latter and thus into said inlet passage.

21. In the combination according to claim 20, a makeup duct connecting the return end of said external circuit with said bypass bore at a location downstream of said bypass valve means to inject make-up fluid into the flow of said pressurized bypass fluid to accelerate said make-up fluid.

22. In the combination according to claim 21, said rotor having a plurality of radially opening notches spaced around its periphery, said pumping elements comprising a corresponding plurality of rollers operable within said notches respectively and adapted to move along said cam surface in fluid sealing engagement therewith, each inlet port having a portion in communication with said inlet passage and also having a portion extending radially inwardly of said cam surface adjacent an axial end of said rotor and communicating axially with said pumping chamber to supply said inlet fluid axially thereinto.

23. In the combination according to claim 22, said bafl le comprising a surface inclined to the flow of pressurized fluid from said bypass bore for directing said flow in a path generally parallel to a plane normal to said rotor axis and inclined both radially inwardly and in a downstream direction within said inlet passage.

24. In the combination according to claim 21, said bypass valve means including a bypass valve bore in said housing substantially parallel to said axis of rotation and perpendicular to said bypass bore, the latter opening into said valve bore at a bypass port upstream of the opening of said make-up duct into said bypass bore.

25. In the combination according to claim 21, said bypass bore entering into a portion of said housing at an exterior opening located radially outwardly of said pumping chamber, said baflle comprising an integral portion of a plug closing said exterior opening and also comprising a surface inclined to the flow of pressurized fluid from said bypass bore for directing said fluid in a path inclined both radially inwardly and in a downstream direction within said inlet passage.

References Cited UNITED STATES PATENTS 2,996,013 8/1961 Thompson et a1. 10342 3,003,423 10/1961 Drutchas 103-42 3,009,420 '11/1961 Livermore et a1 10342 3,025,802 3/1962 Browne 103-42 3,059,580 10/1962 Farrell et al 103-42 3,110,266 11/1963 Livermore 10342 3,236,566 2/1966 Halsey l03136 3,247,803 4/1966 Halsey 103-136 3,253,607 5/1966 Drutchas 10342 DONLEY J. STOCKING, Primary Examiner.

WILBUR I. GOODLIN, Examiner.